Algae provide clues about 600 million years of plant evolution

Liquid samples of Mesotaenium endlicherianum in a laboratory flask, which are about to be combined with fresh medium under sterile conditions. © Janine Fürst-Jansen

 

A research team led by the University of Göttingen has published a study in Nature Plants that delves into the “plant terrestrialization”. In this study, the researchers compared genetic similarities between an alga and terrestrial plants, collected extensive datasets, and developed molecular networks.

The Earth’s surface is covered by plants. They make up the majority of biomass on land and exhibit a wide range of diversity, from mosses to trees. This astounding biodiversity came into existence due to a fateful evolutionary event that happened just once: plant terrestrialization. This describes the point where one group of algae, whose modern descendants can still be studied in the lab, evolved into plants and invaded land around the world. An international research team, led by the University of Göttingen and involving Dr Iker Irissarri, Head of Phylogenetics and Genomics at the Leibniz Institute for the Analysis of Biodiversity Change (LIB), has generated a comprehensive dataset of gene expression for a unicellular alga and derived molecular networks from it. In the process, they identified similarities between the alga Mesotaenium endlicherianum and terrestrial plants. The results have been published in the scientific journal Nature Plants.

Using a strain of Mesotaenium endlicherianum that has been kept safe in the Algal Culture Collection at Göttingen University (SAG) for over 25 years and the unique experimental set-up there, the researchers exposed Mesotaenium endlicherianum to a continuous range of different light intensities and temperatures. Janine Fürst-Jansen, researcher at the University of Göttingen, states: “Our study began by examining the limits of the alga’s resilience – to both light and temperature. We subjected it to a wide temperature range from 8 °C to 29 °C. We were intrigued when we observed the interplay between a broad temperature and light tolerance based on our in-depth physiological analysis.” How the algae respond was not only investigated on a morphological and physiological level, but also by reading the information of about 10 billion RNA snippets. The study used network analysis to investigate the shared behaviour of almost 20,000 genes simultaneously. In these shared patterns, “hub genes” that play a central role in coordinating gene expression in response to various environmental signals were identified. This approach not only offered valuable insights into how algal gene expression is regulated in response to different conditions but, combined with evolutionary analyses, how these mechanisms are common to both land plants and their algal relatives.

Professor Jan de Vries, University of Göttingen, says: “What is so unique about the study is that our network analysis can point to entire toolboxes of genetic mechanisms that were not known to operate in these algae. And when we look at these genetic toolboxes, we find that they are shared across more than 600 million years of plant and algal evolution!” As Armin Dadras, PhD student at the University of Göttingen, explains: “Our analysis allows us to identify which genes collaborate in various plants and algae. It’s like discovering which musical notes consistently harmonize in different songs. This insight helps us uncover long-term evolutionary patterns and reveals how certain essential genetic ‘notes’ have remained consistent across a wide range of plant species, much like timeless melodies that resonate across different music genres.” Iker Irisarri, researcher at LIB emphasizes how this study “uses a powerful cocktail of evolutionary inference, bioinformatics, and big data that allow us to understand how algae and land plants function as individual organisms and how such functions evolved during millions of years.” He finishes saying that “evolutionary genomics is like a fascinating travel back in time, not with a time machine, but with the computer.”

 

Microscope image of one of the closest algal relatives of land plants, a single-celled alga called Mesotaenium endlicherianum (20 micrometres corresponds to 0.02 millimetres). © Tatyana Darienko

 

Original publication
Dadras A, Fürst-Jansen JMR et al. “Environmental gradients reveal stress hubs predating plant terrestrialization”, Nature Plants 2023 DOI: https://doi.org/10.1038/s41477-023-01491-0

Contact
Dr Iker Irisarri
Head of Phylogenetics/Phylogenomics
Centre for Molecular Biodiversity Research (zmb)
Tel.: +49 40 238317-716
E-Mail: i.irisarri@leibniz-lib.de

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